development specification for the feedwater supply assembly · pdf file ·...

Development Specification

for the

Feedwater Supply Assembly (FSA), FSA-431 with

Integrated Auxiliary Feedwater Supply Assembly

(AFSA), FSA-531 Engineering Directorate

Crew and Thermal Systems Division

Verify this is the correct version before use

Date: October 18, 2017

Revision: N/C

CTSD-ADV-1112

National Aeronautics and Space Administration

Lyndon B. Johnson Space Center

Houston, Texas 77058

https://ntrs.nasa.gov/search.jsp?R=20170009946 2018-05-14T07:09:56+00:00Z

ii

CTSD-ADV-1112

Revision N/C

Engineering Directorate

Crew and Thermal Systems Division

National Aeronautics and Space Administration

Lyndon B. Johnson Space Center

Houston, Texas 77058

Development Specification

for the

Feedwater Supply Assembly (FSA),

FSA-431 with Integrated Auxiliary

Feedwater Supply Assembly (AFSA),

FSA-531

Ian Anchondo

FSA Component Lead

Colin Campbell

PLSS Development Team Lead

Development Specification for FSA-431 with Integrated FSA-531 CTSD-ADV-1112

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REVISIONS DATE AUTHOR DESCRIPTION REV. LETTER

6/23/2017 I. Anchondo Initial Release N/C


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TABLE OF CONTENTS

Section Page

Table of Contents .......................................................................................................................................................... 4 Table of Figures ............................................................................................................................................................. 6 Table of Tables .............................................................................................................................................................. 7 1.0 Introduction ....................................................................................................................................................... 8

1.1 Scope ............................................................................................................................................................. 8 1.2 Conventions and Notations ............................................................................................................................ 8

1.2.1 Rationale ................................................................................................................................................ 8 1.2.2 Designations and Prioritization .............................................................................................................. 8

2.0 Documents ......................................................................................................................................................... 8 2.1 Applicable Documents .................................................................................................................................. 8 2.2 Reference Documents .................................................................................................................................... 8

3.0 Feedwater Supply Assembly (FSA) FSA-431/Aux FSA FSA-531 ................................................................... 9 3.1 FSA Description ............................................................................................................................................ 9 3.2 Performance Requirements ............................................................................................................................ 9

3.2.1 Life Performance ................................................................................................................................... 9 3.2.1.1 [R.FSA.001] Operational Fill/Drain Cycles .................................................................................... 9 3.2.1.2 [R.FSA.002] Useful Life ................................................................................................................. 9 3.2.1.3 [R.FSA.003] Shelf Life ................................................................................................................. 10

3.2.2 Material Compatibility......................................................................................................................... 10 3.2.2.1 [R.FSA.004] Feedwater ................................................................................................................ 10 3.2.2.2 [R.FSA.005] Gaseous Nitrogen .................................................................................................... 10 3.2.2.3 [R.FSA.006] Gaseous Oxygen ...................................................................................................... 11

3.2.3 Physical Characteristics ....................................................................................................................... 11 3.2.3.1 [R.FSA.012] FSA Assembly ......................................................................................................... 11 3.2.3.2 [R.FSA.012] FSA INLET/OUT .................................................................................................... 11 3.2.3.3 [R.FSA.013] Restraint Material .................................................................................................... 11 The FSA shall have an outer restraint material. ............................................................................................... 11 3.2.3.4 [R.FSA.014] .................................................................................................................................. 11 3.2.3.5 [R.FSA.020] Mass ........................................................................................................................ 11 3.2.3.6 [R.FSA.021] Volume – Shape Factor ........................................................................................... 11

3.2.4 Feedwater Capacity ............................................................................................................................. 12 3.2.4.1 [R.FSA.007] Feedwater Supply Assembly (FSA-431) ................................................................. 12 3.2.4.2 [R.FSA.008] FSA-431 Ullage ....................................................................................................... 12 3.2.4.3 [R.FSA.009] Auxiliary Feedwater Supply Assembly (FSA-531) ................................................. 12 3.2.4.4 [R.FSA.010] FSA-531 Ullage ....................................................................................................... 12

3.2.5 Pressure Performance .......................................................................................................................... 12 3.2.5.1 [R.FSA.011] Pressure Schedule .................................................................................................... 12

3.2.6 Leak Detection ..................................................................................................................................... 13 3.2.6.1 [R.FSA.016] Low Level Detection ............................................................................................... 13

3.2.7 FSA Construction ................................................................................................................................ 13 3.2.7.1 [R.FSA.014] Bladder Material ...................................................................................................... 13 3.2.7.2 [R.FSA.015] Restraint Material .................................................................................................... 13

3.2.8 Cleanliness ........................................................................................................................................... 14 3.2.8.1 Internal Cleanliness ....................................................................................................................... 14 3.2.8.2 External Cleanliness...................................................................................................................... 14

3.2.9 Passive Characteristics......................................................................................................................... 14 3.2.9.1 [R.FSA.018] Gas Absorption/Permeation..................................................................................... 14 3.2.9.2 [R.FSA.019] Unpressurized Leakage ........................................................................................... 14

3.3 Interface Requirements ................................................................................................................................ 14 3.3.1 [R.FSA.022] Structural ........................................................................................................................ 14 3.3.2 Crew/Human Factors ........................................................................................................................... 14

3.3.2.1 [R.FSA.024] Sharp Edge Limits ................................................................................................... 14 3.4 Maintainability ............................................................................................................................................ 15


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3.4.1 [R.FSA.025] Like-Component Interchangeability............................................................................... 15 3.5 Environments ............................................................................................................................................... 16

3.5.1 Environment Compatibility ................................................................................................................. 16 3.5.1.1 Flammability ................................................................................................................................. 16 3.5.1.2 Toxic Offgassing ........................................................................................................................... 16

3.5.2 Pressure ................................................................................................................................................ 16 3.5.2.1 [R.FSA.026] Ambient Pressure .................................................................................................... 16 3.5.2.2 [R.FSA.027] Ambient Pressure - Launch ..................................................................................... 16

3.5.3 [R.FSA.028] ........................................................................................................................................ 16 3.5.4 [R.FSA.029] Humidity ........................................................................................................................ 16 3.5.5 [R.FSA.030] Gravitational Fields ........................................................................................................ 17 3.5.6 [R.FSA.031] Dynamic Loads .............................................................................................................. 17

Acronyms and Abbreviations ...................................................................................................................................... 18 Definitions ................................................................................................................................................................... 18


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TABLE OF FIGURES

Figure Page Figure 3.2.8-1 – Shape Factors .................................................................................... Error! Bookmark not defined.


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TABLE OF TABLES

Table Page

Table 3.2.1.1-1 – Operating Life ................................................................................................................................... 9 Table 3.2.3.5-1 – PLSS Feedwater Contaminants ....................................................................................................... 10 Table 3.2.4-1 – Pressure Schedule ............................................................................................................................... 13 Table 5.1.4-1 – Gravitational Fields ............................................................................................................................ 17


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1.0 INTRODUCTION

1.1 SCOPE

The FSA with Integrated Aux FSA Specification establishes the requirements for design, performance, and testing

of the FSA-431/FSA-531 assembly in compliance with CTSD-ADV-780, Development Specification for the

Advanced EMU (AEMU) Portable Life Support System (PLSS).

1.2 CONVENTIONS AND NOTATIONS

1.2.1 RATIONALE

A rationale statement is included for each requirement. The purpose of the rationale statement is to indicate why the

requirement is needed, the basis for its inclusion in a requirements document, and to provide context and examples

to stakeholders. It is important to note that a rationale is not binding, and it only provides supporting information.

In the event there is an inconsistency between the requirement and the rationale, the requirement is binding and

takes precedence.

1.2.2 DESIGNATIONS AND PRIORITIZATION

The convention used in this document to indicate requirements, goals, and statements of fact is as follows:

Designation Description

“Shall” used to indicate a requirement which must be implemented and its implementation verified

“Should” used to indicate a goal which must be addressed by the design but is not formally verified

“Will” used to indicate a statement of fact and is not verified

2.0 DOCUMENTS

The documents listed in this section represent the documents that have been identified either in part or in whole

within this document.

2.1 APPLICABLE DOCUMENTS

The applicable documents are documents that have been explicitly identified within requirements statements (i.e.,

“shall” statements) and invoked as technical requirements for implementation. Each requirement statement identifies

the applicable subsections of a document unless it has been deemed appropriate to invoke the entire document.

ASTM D6193 Standard Practice for Stitches and Seams

JPR 5322.1 Contamination Control Requirements

NASA-STD-6016A Standard Materials and Processes Requirements for Spacecraft

NASA-STD-6001B w/CHANGE 2:

Flammability, Odor, Off-gassing, and Compatibility Requirements and Test Procedures for Materials in Environments That Support Combustion

2.2 REFERENCE DOCUMENTS

Documents that are identified but are not invoked within requirements statements are listed below.


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3.0 FEEDWATER SUPPLY ASSEMBLY (FSA) FSA-431/AUX FSA FSA-531

This section contains the technical design and performance requirements for the integrated assembly of the

Feedwater Supply Assembly and Auxiliary Feedwater Supply Assembly for the Advanced EVA Development

Portable Life Support Subsystem (PLSS).

3.1 FSA DESCRIPTION

Although the integrated FSA will be located within the Space Suit Assembly (SSA), its function is integral in the

performance of Portable Life Support functions:

FSA-431

Stores feedwater used to provide makeup water to the thermal loop as it is consumed by the SWME, HX-

440 in the evaporative cooling process

Material compliancy allows suit pressure to provide pressurization of the thermal control loop at the pump

inlet.

Provides low level detection to enable a controlled EVA termination without the reliance of redundant

systems under most operations concepts

FSA-531

Stores feedwater used to provide makeup water to the thermal loop as it is consumed by the HX-550.

Material compliancy allows suit pressure to provide pressurization of the thermal control loop at the pump

inlet.

3.2 PERFORMANCE REQUIREMENTS

3.2.1 LIFE PERFORMANCE

3.2.1.1 [R.FSA.001] OPERATIONAL FILL/DRAIN CYCLES

The FSA shall have an operating life as specified in Table 3.2.1.1.-1:

Component Function Cycles

(minimum)

Minimum

Duration (hrs)

Pressure Cycle Fill*/Drain Cycles

*Fill to MEOP

400(1,2) ---

Table 3.2.1.1-1 – Operating Life

Rationale: The goal is to make the hardware and its associated certification “robust-enough” such that detailed

tracking of operating cycles and the resultant operational over-head is not required.

(1) This is based on one cycle per EVA for 100 EVAs and a scatter factor of 4 as derived from operational

concepts covered in CTSD-ADV-959.

(2) A cycle is defined as the process of going from a discharged state (ullage volume remaining) to a fully

charged state at MEOP and then back to a discharged state (ullage volume remaining).

(3) Although the number of cycles really only applies to the FSA-431 component of the integrated

assembly, it makes little sense to reduce the number for FSA-531 which will be of similar construction

and will need to demonstrate robustness as it is a redundant life support system component.

3.2.1.2 [R.FSA.002] USEFUL LIFE

The FSA shall have a useful life of 5 years minimum without refurbishment assuming that the usage rate does not

exceed operational life (Para 3.2.1.1).

Rationale: This provides a tracking clock from the time wetted service is started and is considered the total “life

time” from birthdate of the hardware.


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3.2.1.3 [R.FSA.003] SHELF LIFE

The FSA shall have a shelf-life of 10 years minimum.

Rationale: This allows for program logistics flexibility without recertification.

3.2.2 MATERIAL COMPATIBILITY

3.2.2.1 [R.FSA.004] FEEDWATER

The FSA shall be compatible and operate using water per JSC-SPEC-C-20D, Grade B with the added contaminants

totaling the amounts dictated in Table 3.2.3.5-1.

Contaminant Amount (mg/L)

Barium 0.1

Calcium 1.0

Chlorine 5.0

Chromium 0.05

Copper 0.5

Iron 0.2

Lead 0.05

Magnesium 1.0

Manganese 0.05

Nickel 0.05

Nitrate 1.0

Potassium 5.0

Sulfate 5.0

Zinc 0.5

Organics

Total Acids 0.5

Total Alcohols 0.5

Total Organic Carbon 0.3

Table 3.2.3.5-1 – PLSS Feedwater Contaminants

Rationale: The table was generated with margin based on the capabilities of the International Space Station Water

Processor Assembly (WPA). The potable water requirements specified per SSP 41000, Table LVI convey

the Spacecraft Maximum Allowable Concentrations (SMAC) that can be tolerated by a human for long

durations whereas the included table seeks to require performance with water that includes contaminants

reasonable to expect a spacecraft to deliver to the PLSS. This satisfies AEMU PTRS requirement, R1.311.

3.2.2.2 [R.FSA.005] GASEOUS NITROGEN

The FSA shall be compatible and operate using gaseous nitrogen per MIL-PRF-27401F, Performance Specification

for Propellant Pressurizing Agent, Nitrogen, Type I, Grade B as a test fluid.

Rationale: Gaseous nitrogen provides a safe testing fluid and will be used as a pressurant on the outside of the FSA

bladder.


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3.2.2.3 [R.FSA.006] GASEOUS OXYGEN

The FSA shall be compatible and operate using gaseous oxygen per MIL-PRF-27210G, Performance Specification

for Oxygen, Aviators Breathing, Liquid and Gas, Type I as the working fluid.

Rationale: Gaseous oxygen is required for human metabolism; gaseous form storage of oxygen is the basis for the

current PLSS design approach (CTSD-ADV-959). Gaseous oxygen will be used on the outside of the FSA

bladder as a pressurant in the manned or flight configuration.

3.2.3 PHYSICAL CHARACTERISTICS

3.2.3.1 [R.FSA.007] FSA ASSEMBLY

The FSA shall be made up of modular bladders that can be connected or disconnected from the larger assembly.

Rationale: Different size bladders will make up the total FSA assembly and therefore will require the need to mix

and match sizing to make up the total FSA mass.

3.2.3.2 [R.FSA.008] MODULAR BLADDERS

The FSA modular bladders shall have an inlet and outlet connection.

Rationale: The design should be able to purge water in and out to enable the sampling of water.

3.2.3.3 [R.FSA.009] RESTRAINT MATERIAL

Each modular bladder shall have an outer restraint material.

Rationale: FSA Prototyping has proven to benefit from a two-layer construction with the bladder withholding the

water and the restraint up taking the pressure load. The aggregate will make up the FSA system.

3.2.3.4 [R.FSA.010]

The FSA shall have 10 Fill/Drain cycles prior to performing Acceptance Testing to ensure the stability bladder

material to the restraint material.

Rationale: Prototype testing has shown the need to “break-in” the bladder before a steady-state volume of water is

defined.

3.2.3.5 [R.FSA.011] MASS

The FSA shall have a total dry mass less than .23 kg [0.5 lbm].

Rationale: This is the basic allocation provided in the MEL.

3.2.3.6 [R.FSA.012] VOLUME – SHAPE FACTOR


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The FSA modular bladders shall not exceed a width of more than 12 inches.

Rationale: The maximum width allocated in the suit currently is about 12 inches in width therefore cannot exceed in

that dimension.

3.2.4 FEEDWATER CAPACITY

3.2.4.1 [R.FSA.013] FEEDWATER SUPPLY ASSEMBLY (FSA-431)

The FSA shall provide a minimum usable feedwater quantity of 4.5 kg [10 lbm].

Rationale: This number is currently in-flux based on Qmet, environmental heat leak, and avionics waste heat, but

the range is well vetted with historical suit systems: Shuttle/ISS EMU = 9.2 lbs H2O in the combined

primary and reserve feedwater tanks and Apollo EMU = 11.9 lbs H2O with the combined primary and

auxiliary feedwater bladders on the -7 PLSS. This satisfies the intent of the AEMU PTRS requirement,

R1.309.

3.2.4.2 [R.FSA.014] FSA-431 ULLAGE

The FSA-431 shall have an ullage below 5% of the mass per individual bladder.

Rationale: Overfilling the bladders to achieve the necessary usable water is not desired above 0.5 lb of the total

mass.

3.2.4.3 [R.FSA.015] AUXILIARY FEEDWATER SUPPLY ASSEMBLY (FSA-531)

The FSA-531 shall provide a minimum usable auxiliary feedwater quantity of .45 kg [1 lbm].

Rationale: This number is based on the initial sizing for the auxiliary thermal loop documented in ESCG-4470-12-

TEAN-DOC-0019. For this condition, with an allowable heat storage of 300 BTU, a thermally neutral

environment (0 heat leak), an average metabolic rate of 1200 BTU/hr, a 2 acfm ventilation flowrate, and a

60 minute duration, the needed water quantity was .32 kg [0.7 lbm] of water.

Item Feedwater

kg [ lbm]

Feedwater required for design point:

o 1200 BTU/hr

o 60 minute retreat

o Thermal environment: neutral

o 2 acfm flowrate

0.32 [0.7]

LCVG water charge estimated for core only .14 [0.3]

Total Usable: .45[1.0]

This does not include the ullage quantity that varies with design of the FSA itself.

3.2.4.4 [R.FSA.016] FSA-531 ULLAGE

The FSA-531 shall have an ullage below 5% of the mass per individual bladder.

Rationale: Overfilling the bladders to achieve the necessary usable water is not desired above 0.5 lb of the total

mass

3.2.5 PRESSURE PERFORMANCE

3.2.5.1 [R.FSA.017] PRESSURE SCHEDULE


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The FSA shall have a pressure schedule as defined in Table 3.2.4-1.

Operating Pressure Pressure

kPa (diff)

[psid]

Maximum Design Pressure (MDP) (2) 180

[26.1]

Proof Pressure (1.5 x MDP) (1) 270

[39.2]

Burst Pressure (2.5 x MDP) (1) 450

[65.3]

Table 3.2.4-1 – Pressure Schedule

Rationale:

(1) 785BThis satisfies Table 3.3.1-1 (Minimum Factors of Safety for Pressure) Sub para 3.D (Actuating

cylinders, valve, etc.) in SSP 30559, ISS Structural Design and Verification Requirements.

(2) This represents the following pressure stack-up for the primary thermal loop (FSA-431) with the

auxiliary thermal loop (FSA-531) sufficiently less in operation but benefitting from the robustness of

the primary design:

Condition/Source Pressure

Maximum charging pressure from vehicle with multiple levels of over-pressure

protection

15 psid

Cabin reference pressure for the feedwater recharge supply 15.2 psia

Lowest suit pressure in which a vacuum feedwater recharge would be performed -4.3psia

31.1 psid

Maximum Design Pressure (MDP) 25.9 psid

3.2.6 LEAK DETECTION

3.2.6.1 [R.FSA.018] LOW LEVEL DETECTION

The FSA shall be isolate 1.5 lb of water with a 0.5 psid +/-0.05 check valve.

Rationale: The need to discern the last 1.5 lb of cooling is necessary to determine an unexpected leak or a higher

than expected metabolic load without the insight of Mission Control to provide insight.

3.2.7 FSA CONSTRUCTION

3.2.7.1 [R.FSA.019] BLADDER MATERIAL

The FSA bladders shall be made from Teflon FEP or Flourel.

Rationale: Bladder materials interfacing with EMU Thermal Systems are either Teflon FEP or Flourel.

3.2.7.2 [R.FSA.020] RESTRAINT MATERIAL

FSA Restraint shall be made of a breathable material with wicking capability.

Rationale: The restraint layer should not hold water to the level where microbial growth can occur in a closed

humid environment.


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3.2.8 CLEANLINESS

3.2.8.1 [R.FSA.021]INTERNAL CLEANLINESS

The FSA shall meet Level 150A cleanliness as defined per JPR 5322.1G.

Rationale: Same cleanliness level as the rest of the loop.

3.2.8.2 [R.FSA.022]EXTERNAL CLEANLINESS

The FSA shall be clean to VC+UV as defined per JPR 5322.1G.

Rationale: Due to the potential of a wetted external surface, the presence of hydrocarbons shall be kept to a

minimum to avoid microbial grown. UV provides a level of verification.

3.2.9 PASSIVE CHARACTERISTICS

3.2.9.1 [R.FSA.023] GAS ABSORPTION/PERMEATION

The FSA shall limit the amount of gas that either enters or leaves the bladder volume to 5 sccm.

Rationale:

3.2.9.2 [R.FSA.024] UNPRESSURIZED LEAKAGE

The FSA shall limit external leakage to 9.56E-11 kg/sec [7.59E-07 pph] maximum at a pressure of 29.6 kPa [4.3

psia] regardless of orientation.

Rationale: The FSA shall not leak during EVA or quiescent operations.

3.3 INTERFACE REQUIREMENTS

3.3.1 STRUCTURAL

3.3.1.1 [R.FSA.025] SUIT INTERFACE

The FSA shall have the necessary attachment to allow for hard mount to the suit hatch volume.

Rationale: Although undefined the FSA assembly will be attached to the suit volume attached to the hatch space.

3.3.2 CREW/HUMAN FACTORS

3.3.2.1 [R.FSA.026] SHARP EDGE LIMITS

The FSA should comply with the Corners and Edges limits established in Table 3.3.2.5-1.


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Table 3.3.2.5-1 – Corners and Edges

Rationale: The NASA-STD-3001, Vol II, [V2 9009], Sharp Corners and Edges – Fixed requires this for Crew

interfaces.

3.4 MAINTAINABILITY

3.4.1 INTERCHANGEABILITY

3.4.1.1 [R.FSA.027] MODULAR BLADDER INTERCHANGEABILITY

The FSA shall be interchangeable with any other unit of the same part number.

Rationale: The definition as provided in JSC EA-WI-027 is as follows:

Two or more parts are interchangeable when they possess such physical and functional characteristics as to be

equivalent in performance and durability, and are capable of being exchanged one for another without

alteration of the items themselves or adjoining items. Functional and physical characteristics, which

would constitute interchangeability, are:

Parts must have the same design envelope and have no limitations imposed on use.


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Parts must utilize the same attachments, mountings or mating surfaces. Attachments, connectors,

wiring, ground support equipment, and tubing must be the same to the extent that no re-work is

required on installation.

Parts must meet all baselined design requirements for performance and durability. Performance

or durability design requirements include the same safety, strength, electrical, mechanical,

reliability, maintainability, tolerance, and weight and center of gravity requirements.

Parts must have the same adjustments, testing, operations, and maintenance requirements and

design to the extent that the same test procedures, specifications, and operating procedures have

been and/or may be utilized.

3.5 INDUCED ENVIRONMENTS

3.5.1 ENVIRONMENT COMPATIBILITY

3.5.1.1 [R.FSA.028] FLAMMABILITY

The FSA shall meet flammability standards as specified in NASA-STD-6001, Flammability, Odor, Off-gassing and

Compatibility Requirements and Test Procedures for Materials in Environments that support Combustion.

3.5.1.2 [R.FSA.029] TOXIC OFF-GASSING

The FSA shall not have any toxic off-gassing as specified in NASA-STD-6001, Flammability, Odor, Off-gassing

and Compatibility Requirements and Test Procedures for Materials in Environments that support Combustion.

3.5.2 PRESSURE

3.5.2.1 [R.FSA.030] AMBIENT PRESSURE

The FSA shall operate in a pressure environment ranging from 3.5 psia to 23.1 psia.

3.5.2.2 [R.FSA.031] AMBIENT PRESSURE - LAUNCH

The FSa, in a stowed configuration, shall operate after exposure to a pressure environment ranging from 0.0 to 130

kPa [0.0 to 18.8 psia].

3.5.3 [R.FSA.032]

3.5.4 [R.FSA.033] HUMIDITY

The FSA shall operate in an environment with Relative Humidity (RH) cycling between 30 + 10% and 80 + 10% for

ten 24 hr cycles per MIL-STD-810G, Method 507.5, Induced Cycle B3.


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3.5.5 [R.FSA.034] GRAVITATIONAL FIELDS

The FSA shall operate in the gravitational fields defined in Table 5.1.4-1 in any orientation.

Environment Gravity Field (g)

Terrestrial 1

Lunar 0.17

Mars 0.38

LEO ~0

Table 5.1.4-1 – Gravitational Fields

Rationale: The PLSS must perform in a variety of gravity fields to meet system performance requirements across all

of the applicable environments. This satisfies the intent of AEMU PTRS requirements, R1.016 and R1.017.

3.5.6 [R.FSA.034] DYNAMIC LOADS

Reference CTSD-ADV-780, Para 5.1.5.


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ACRONYMS AND ABBREVIATIONS

CTSD Crew and Thermal Systems Division

EMU Extravehicular Mobility Unit

EV Extra-Vehicular

EVA Extravehicular Activity

GOX Gaseous Oxygen

GSE Ground Support Equipment

ISS International Space Station

IV Intra-Vehicular

IVA Intra-Vehicular Activity

JSC Johnson Space Center

KOZ Keep Out Zone

MEOP Maximum Expected Operating Pressure

NASA National Aeronautics and Space Administration

PLSS Primary Life Support System or Portable Life Support System

PPRV Positive Pressure Relief Valve

RH Relative Humidity

SSA Space Suit Assembly

TBD To Be Defined

DEFINITIONS

STP Standard Temperature and Pressure (STP)

The STP reference for all mass-referenced volumetric flows discussed here-in shall be

that as defined by the National Institute of Standards and Technology (NIST)

Pressure = 1 atm = 14.676 psia = 101.325kPa

Temperature = 0C = 273.15K = 32F